A growing body of evidence that has emerged in recent years suggests that stray mastiffs on the Tibetan Plateau — including parts of the Tibet Autonomous Region in China’s southwest and Qinghai province in the northwest — are encroaching on snow leopards’ habitats and taking their food.

Conservationist Yin Hang was quick to spot the trend. While reviewing video footage shot by a Tibetan Buddhist lama in 2014, Yin came across a shocking scene: three enormous Tibetan mastiffs cornering a snow leopard in an effort to steal the leopard’s prey, a Himalayan blue sheep. The victory went to the dogs, who forced the snow leopard to retreat.

The [ecological] balance has been disrupted.

- Yin Hang, conservationist

Yin, founder of the sustainable development-focused nongovernmental organization Gangri Neichog Research and Conservation Center in Qinghai, describes free-roaming mastiffs as an “alien invasive species” that poses a threat to snow leopards and to the plateau’s vulnerable ecosystem.

“Many of them have been abandoned and roam freely in the wilderness,” says Yin, referring to the dogs. “The [ecological] balance has been disrupted,” she adds.

Researchers estimate that there are likely no more than 6,390 snow leopards left in the world. Habitat loss, poaching, climate change, and human activity such as mining and road construction already pose significant threats to the species.

For centuries, Tibetan herders have raised mastiffs, one of the largest dog breeds native to the plateau, to protect their yaks and sheep from wolves and other predators. According to researchers, the dogs’ origins can be traced back over tens of thousands of years to the gray wolf.

The source of the current problem lies in the boom in popularity of Tibetan mastiffs, which reached its zenith around 2010. Demand for the breed skyrocketed, as people around China forked out huge sums of money to purchase the thick-furred, bearlike animals.

Gage, a 51-year-old Tibetan craftsman, tells Sixth Tone he was first drawn to the mastiff-breeding business back in 2005. “I started to raise a lot more of them — 18 at my peak — and tried to sell them to other provinces,” he says.

Many of Gage’s customers were from places in eastern China, such as Shandong province, or from Beijing in the north. One of his dogs sold for 2 million yuan (about $292,000).

In the Yushu Tibetan Autonomous Prefecture, southwestern Qinghai — a region famous for producing high-quality Tibetan mastiffs — almost every family raised mastiffs to sell back then, says Yin.

But as China’s economy slowed, and a government austerity drive increasingly discouraged conspicuous displays of wealth, demand for Tibetan mastiffs waned. The resulting oversupply of the animals led to an increase in the number of abandoned mastiffs.

The elderly and the youth didn’t dare to walk the streets alone because there were too many stray dogs, and people often got bitten.

- Zhaxi, Tibetan lama

Some locals have attempted to address the issue. Zhaxi, a lama serving as a steward at Surmang Monastery in Yushu, recalls seeing many stray mastiffs in the town over the years. “The elderly and the youth didn’t dare to walk the streets alone because there were too many stray dogs, and people often got bitten,” he tells Sixth Tone. Early last year, he and other lamas proposed that the local government construct a pound for unwanted dogs, and they soon raised around 500,000 yuan for the project.

These days, nearly a thousand desexed stray mastiffs are housed in a pound surrounded by iron fences. The monastery barely has enough money to feed so many dogs, so staff collect leftover food from nearby villages and mix it with highland barley to feed them once a day.

The Yushu government announced in July 2016 that it had built five dog pounds and provided shelter for around 5,000 stray mastiffs. Yet the dogs still roam freely in many other remote areas.

A mastiff walks by a group of other mastiffs in Yushu Tibetan Autonomous Prefecture, Qinghai province, Dec. 10, 2016. Shi Yi/Sixth Tone

Wang Yunxiang, a conservationist at the Chinese NGO Shanshui Conservation Center, has studied the stray mastiffs’ diet. His analysis of the dogs’ feces indicates that 80 percent of their food is made up of herders’ livestock. The remaining 20 percent comprises small wild animals, especially Himalayan blue sheep.

Researches are also concerned that stray dogs could spread diseases to wild animals, as well as to humans. In Tanzania in the mid-1990s, for example, wild lions were almost wiped out after being struck with an infectious disease thought to have been transmitted by dogs.

The desire to do her part to protect the delicate environment of the Tibetan Plateau prompted Yin to establish the Gangri Neichog Research and Conservation Center two years ago. Having worked to resolve the stray mastiff issue, the center is now making a documentary to increase awareness of the mastiffs’ plight. The organization also plans to fund a program to desex free-roaming mastiffs in remote regions without access to veterinary services.

“We hope different groups, communities, NGOs, and government bodies can work together to solve the problem,” she tells Sixth Tone.